`socketserver` --- 用於網路伺服器的框架¶

socketserver 模組簡化了編寫網路伺服器的任務。

此模組在 WebAssembly 平台上不起作用或無法使用。更多資訊請參閱 WebAssembly 平台。

There are four basic concrete server classes:

class socketserver.TCPServer(server_address, RequestHandlerClass, bind_and_activate=True)¶: This uses the internet TCP protocol, which provides for continuous streams of data between the client and server. If bind_and_activate is true, the constructor automatically attempts to invoke server_bind() and server_activate(). The other parameters are passed to the BaseServer base class.

class socketserver.UDPServer(server_address, RequestHandlerClass, bind_and_activate=True)¶: This uses datagrams, which are discrete packets of information that may arrive out of order or be lost while in transit. The parameters are the same as for TCPServer.

class socketserver.UnixStreamServer(server_address, RequestHandlerClass, bind_and_activate=True)¶
class socketserver.UnixDatagramServer(server_address, RequestHandlerClass, bind_and_activate=True)¶: These more infrequently used classes are similar to the TCP and UDP classes, but use Unix domain sockets; they're not available on non-Unix platforms. The parameters are the same as for TCPServer.

These four classes process requests synchronously; each request must be completed before the next request can be started. This isn't suitable if each request takes a long time to complete, because it requires a lot of computation, or because it returns a lot of data which the client is slow to process. The solution is to create a separate process or thread to handle each request; the ForkingMixIn and ThreadingMixIn mix-in classes can be used to support asynchronous behaviour.

Creating a server requires several steps. First, you must create a request handler class by subclassing the BaseRequestHandler class and overriding its handle() method; this method will process incoming requests. Second, you must instantiate one of the server classes, passing it the server's address and the request handler class. It is recommended to use the server in a with statement. Then call the handle_request() or serve_forever() method of the server object to process one or many requests. Finally, call server_close() to close the socket (unless you used a with statement).

When inheriting from ThreadingMixIn for threaded connection behavior, you should explicitly declare how you want your threads to behave on an abrupt shutdown. The ThreadingMixIn class defines an attribute daemon_threads, which indicates whether or not the server should wait for thread termination. You should set the flag explicitly if you would like threads to behave autonomously; the default is False, meaning that Python will not exit until all threads created by ThreadingMixIn have exited.

Server classes have the same external methods and attributes, no matter what network protocol they use.

Server Creation Notes¶

There are five classes in an inheritance diagram, four of which represent synchronous servers of four types:

+------------+
| BaseServer |
+------------+
      |
      v
+-----------+        +------------------+
| TCPServer |------->| UnixStreamServer |
+-----------+        +------------------+
      |
      v
+-----------+        +--------------------+
| UDPServer |------->| UnixDatagramServer |
+-----------+        +--------------------+

Note that UnixDatagramServer derives from UDPServer, not from UnixStreamServer --- the only difference between an IP and a Unix server is the address family.

class socketserver.ForkingMixIn¶

class socketserver.ThreadingMixIn¶

Forking and threading versions of each type of server can be created using these mix-in classes. For instance, ThreadingUDPServer is created as follows:

class ThreadingUDPServer(ThreadingMixIn, UDPServer):
    pass

The mix-in class comes first, since it overrides a method defined in UDPServer. Setting the various attributes also changes the behavior of the underlying server mechanism.

ForkingMixIn and the Forking classes mentioned below are only available on POSIX platforms that support fork().

block_on_close¶

ForkingMixIn.server_close waits until all child processes complete, except if block_on_close attribute is False.

ThreadingMixIn.server_close waits until all non-daemon threads complete, except if block_on_close attribute is False.

max_children¶: Specify how many child processes will exist to handle requests at a time for ForkingMixIn. If the limit is reached, new requests will wait until one child process has finished.

daemon_threads¶: For ThreadingMixIn use daemonic threads by setting ThreadingMixIn.daemon_threads to True to not wait until threads complete.

在 3.7 版的變更: ForkingMixIn.server_close and ThreadingMixIn.server_close now waits until all child processes and non-daemonic threads complete. Add a new ForkingMixIn.block_on_close class attribute to opt-in for the pre-3.7 behaviour.

class socketserver.ForkingTCPServer¶
class socketserver.ForkingUDPServer¶
class socketserver.ThreadingTCPServer¶
class socketserver.ThreadingUDPServer¶
class socketserver.ForkingUnixStreamServer¶
class socketserver.ForkingUnixDatagramServer¶
class socketserver.ThreadingUnixStreamServer¶
class socketserver.ThreadingUnixDatagramServer¶: These classes are pre-defined using the mix-in classes.

在 3.12 版被加入: The ForkingUnixStreamServer and ForkingUnixDatagramServer classes were added.

To implement a service, you must derive a class from BaseRequestHandler and redefine its handle() method. You can then run various versions of the service by combining one of the server classes with your request handler class. The request handler class must be different for datagram or stream services. This can be hidden by using the handler subclasses StreamRequestHandler or DatagramRequestHandler.

Of course, you still have to use your head! For instance, it makes no sense to use a forking server if the service contains state in memory that can be modified by different requests, since the modifications in the child process would never reach the initial state kept in the parent process and passed to each child. In this case, you can use a threading server, but you will probably have to use locks to protect the integrity of the shared data.

On the other hand, if you are building an HTTP server where all data is stored externally (for instance, in the file system), a synchronous class will essentially render the service "deaf" while one request is being handled -- which may be for a very long time if a client is slow to receive all the data it has requested. Here a threading or forking server is appropriate.

In some cases, it may be appropriate to process part of a request synchronously, but to finish processing in a forked child depending on the request data. This can be implemented by using a synchronous server and doing an explicit fork in the request handler class handle() method.

Another approach to handling multiple simultaneous requests in an environment that supports neither threads nor fork() (or where these are too expensive or inappropriate for the service) is to maintain an explicit table of partially finished requests and to use selectors to decide which request to work on next (or whether to handle a new incoming request). This is particularly important for stream services where each client can potentially be connected for a long time (if threads or subprocesses cannot be used).

Server Objects¶

class socketserver.BaseServer(server_address, RequestHandlerClass)¶

This is the superclass of all Server objects in the module. It defines the interface, given below, but does not implement most of the methods, which is done in subclasses. The two parameters are stored in the respective server_address and RequestHandlerClass attributes.

fileno()¶: Return an integer file descriptor for the socket on which the server is listening. This function is most commonly passed to selectors, to allow monitoring multiple servers in the same process.

handle_request()¶: Process a single request. This function calls the following methods in order: get_request(), verify_request(), and process_request(). If the user-provided handle() method of the handler class raises an exception, the server's handle_error() method will be called. If no request is received within timeout seconds, handle_timeout() will be called and handle_request() will return.

serve_forever(poll_interval=0.5)¶: Handle requests until an explicit shutdown() request. Poll for shutdown every poll_interval seconds. Ignores the timeout attribute. It also calls service_actions(), which may be used by a subclass or mixin to provide actions specific to a given service. For example, the ForkingMixIn class uses service_actions() to clean up zombie child processes.

在 3.3 版的變更: Added service_actions call to the serve_forever method.

service_actions()¶: This is called in the serve_forever() loop. This method can be overridden by subclasses or mixin classes to perform actions specific to a given service, such as cleanup actions.

在 3.3 版被加入.

shutdown()¶: Tell the serve_forever() loop to stop and wait until it does. shutdown() must be called while serve_forever() is running in a different thread otherwise it will deadlock.

server_close()¶: Clean up the server. May be overridden.

address_family¶: The family of protocols to which the server's socket belongs. Common examples are socket.AF_INET,

socketserver --- 用於網路伺服器的框架¶

Server Creation Notes¶

Server Objects¶

`socketserver` --- 用於網路伺服器的框架¶